The overview of the analytic and experimental work related to the Halden LOCA test in IFA-650.7 with a fuel segment pre-irradiated in the BWR KKL is presented. The test was carried out at Halden after preliminary design analysis - using the EPRI’s Falcon code - at PSI. The post-test calculation is performed using the factual boundary conditions of the test, and the results are compared with the experimental data available. Despite some deviations from the prescribed experimental procedure, the major requirements for the conditions of cladding burst have been observed in the test. Specifically, the main recommendation regarding test-rod design, i.e. the use of gas fill-pressure of 6 bar (RT), was employed, which had predefined the condition of cladding rupture to occur at a relatively high temperature: around 1050°C. As predicted, the peak local hoop strain of the deformed cladding - observed by the PIE - is low enough to avoid a mechanical contact of the heater and cladding, while the increase of the integral void volume in the rod seems to be large enough to surpass the empiric threshold for the onset of the axial fuel relocation. Moreover, for the first time in the Halden-LOCA experimental series, an extensive local oxidation and hydrogen uptake have been found by the PIE on the inner surface of the cladding - around the burst area.
As the post-test analysis shows, a cladding-strain profile similar to measured one is calculated for a critical damage-index (DI) less than unity, i.e. 0.6-0.7, which is argued to result from premature spraying, switched on before the cladding rupture. A hypothesis is thus put forward that such spraying could have resulted in additional azimuthal non-uniformity of the distribution of cladding temperature, which is typical of real LOCA conditions prevailing in a fuel-assembly in comparison to the ones of single-rod experiments.